Method and system for corn fractionation

ABSTRACT

Methods and apparatus for processing corn into one or more corn products. Zein is extracted from corn or corn products or by-products with a solvent. The corn-solvent mixture is separated into streams, one of which preferably includes an extract containing at least zein and solvent, and another that contains de-zeined corn solids and adsorbed solvent. The solvent is separated from the zein, and the de-zeined, desolventized corn solids are processed to provide one or more corn products.

PRIORITY CLAIM

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/327,166, filed Jan. 6, 2006, which claims the benefit ofU.S. Provisional Application Ser. No. 60/641,664, filed Jan. 6, 2005,under 35 U.S.C. § 119.

FIELD OF THE INVENTION

The present invention relates generally to corn fractionation processesand equipment. The invention specifically concerns production of one ormore corn products, such as industrial, food, feed, and/or kindredproducts, from corn.

BACKGROUND OF THE INVENTION

Dry milling, in which whole corn is ground or milled to produce productsfor feed and food uses, is a popular method in the art for processingcorn. However, dry milling is typically restricted in its range ofproducts, and it typically is not designed to separate the individualcomponents of corn, except in certain methods wherein the corn ispartially degerminated prior to milling.

Another method of processing corn is the dry-grind ethanol process,which conventionally includes dry-grinding whole corn, and addingenzymes and yeast to the cooked corn to produce primarily fuel ethanol.Yet another method is corn wet milling, which produces corn oil, corngluten feed, corn gluten meal, starch, fiber, and corn steep liquor.

Conventional dry-grind and wet milling have limitations. For example,products of conventional dry-grind ethanol processing typically arelimited to ethanol, carbon dioxide, and distillers dried grains withsolubles (DDGS). Of these products, DDGS is a low-value animal feed,carbon dioxide has an even lower value and is often merely discharged tothe atmosphere, and ethanol, if used for fuel, competes unfavorably withlow-priced petroleum products. Thus, the dry-grind ethanol industrypresently needs government subsidies and tax waivers, which are likelyto be eliminated, for economic survival.

In wet milling, corn is first soaked in water (steeped) for severalhours prior to undergoing a series of grinding and separation steps thatresult in one or more of several products such as corn oil, starch, corngluten feed, corn gluten meal, fiber, and corn steep liquor. Corn wetmilling produces a multitude of high value products, but requires highcapital investments in plant and machinery. It also requires largeamounts of water, typically 5-9 gallons per bushel of corn, primarilyfor the purification of starch and for steeping.

The required steeping of corn in conventional wet milling istime-consuming. For typical steeping, corn is soaked in water at about50° C. and for 22-50 hours. Sulfur dioxide is added, and lactic acid isproduced by bacteria. Steeping is done mainly to facilitate a subsequentseparation of the germ that contains the oil.

Additionally, the water from the above steeping step (“steep water”) isdilute and has to be evaporated. This requires a significant amount ofenergy. The evaporated steep water (“corn steep liquor”) is sold as suchor added to the corn gluten feed, which is a low-value animal feed.

SUMMARY OF THE INVENTION

Methods and apparatus for fractionation of corn are provided. In anexample method, zein is extracted from corn or corn products orby-products with a solvent. The corn-solvent mixture is separated intostreams, one of which preferably includes an extract containing at leastzein and solvent, and another that contains de-zeined corn solids andadsorbed solvent. The solvent is separated from the zein, and thede-zeined, desolventized corn solids are processed to provide one ormore corn products.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the invention will be apparentto those skilled in the art from the following detailed description andby reference to the drawings, of which:

FIG. 1 is a schematic diagram showing steps in an example process forcorn fractionation to produce one or more of corn oil, fiber, corngluten meal and starch according to an embodiment of the presentinvention;

FIG. 2 is a schematic diagram showing steps in an example process forcorn fractionation to produce one or more of corn oil, zein, fiber, corngluten meal and starch according to an embodiment of the presentinvention; and

FIG. 3 is a schematic diagram showing steps in an example process forcorn fractionation to produce one or more of zein, fiber, high-oil corngluten meal and starch according to another embodiment of the presentinvention.

DETAILED DESCRIPTION

Preferred embodiments of the present invention provide a method of cornfractionation, and more particularly a method of processing corn intoindustrial, food, feed, and/or kindred products. A preferred processovercomes several limitations of conventional corn wet milling processesby eliminating the steeping and germ handling steps, and by reducingfresh water usage.

Generally, in certain example methods, oil is extracted from corn orcorn products or by-products with a solvent. The corn-solvent mixture isseparated into streams, one of which preferably includes an extractcontaining at least oil and solvent, and another containing de-oiledcorn solids and adsorbed solvent. The solvent is separated from oil, andthe de-oiled, desolventized corn solids are processed to provide one ormore corn products.

More particularly, in a preferred method, corn is dry-ground and reactedwith organic solvent to extract oil. The oil is separated from theresultant extract and recovered from the extract using membranetechnology. Zein may also be produced if the solvent is ethanol, forexample. The de-oiled meal is subjected to a series of grinding andseparation operations such as centrifugation, hydryocyclones, and/ormembrane technology to result in one or more additional products such ascorn products, corn gluten meal, corn starch, and fiber. Zein may alsobe recovered by re-extracting the de-oiled meal with aqueous ethanol andultrafiltering the extract.

In other example methods, zein is extracted from corn or corn productsor by-products with a solvent. The corn-solvent mixture is separatedinto streams, one of which preferably includes an extract containing atleast zein and solvent, and another containing de-zeined corn solids andadsorbed solvent. The solvent may be separated from the zein. Thede-zeined, desolventized corn solids are processed to provide one ormore corn products.

In a more particular example of this latter method, corn is dry-ground(e.g., grinding or dry-milling) and reacted with organic solvent toextract zein. A de-zeined meal is desolventized to provide de-zeined,desolventized corn solids, which undergo separation operations such as,but not limited to, fiber separation and washing to provide fiber,starch separation to provide starch, and gluten thickening to provide ahigh-oil protein, such as high-oil corn gluten meal. Remaining solidsmay be recycled to upstream operations, such as but not limited tofurther starch separation or gluten thickening.

A method that eliminates the steeping process, and yet produces corn oilwith equivalent or greater yields and without the production or handlingof germ, has been described in U.S. Pat. No. 6,433,146 to the presentinventor, which is incorporated herein by reference. The '146 patentdescribes a method of obtaining corn oil using an organic solvent suchas ethanol to extract the oil, followed by a primary separation step tofilter the extract and a subsequent membrane separation to concentratethe oil in the extract and to recycle the solvent. The de-oiled cornsolids residue from the primary separation step is one subject of thisinvention in certain example embodiments.

Alternatively or additionally, zein protein may be partially orsubstantially extracted using an ethanol extraction, separation andmembrane separation. The zein-free corn solids, or alternatively thede-oiled zein-free corn solids, are processed by embodiments of thisinvention.

In an exemplary practice of this invention, the de-oiled corn solids aremixed with process water to create a suspension including starch, fiberand protein. It is subjected to grinding and separation steps toseparate the fiber from the starch and protein. The fiber is washed anddried, and the fiber wash water is recycled as process water or membranefiltered to recover the protein and starch. Then, the starch-proteinsuspension is subjected to an optional concentration step followed by aseparation step to separate the starch from the protein. The proteinfraction, containing some starch, is thickened and dewatered prior todrying. The starch is purified by washing with fresh water. The washwater containing the impurities is simultaneously separated from thestarch. This wash water is used as process water or is subjected tomembrane clarification and concentration to enable it to be recycled asstarch wash water and to recover the solids.

According to preferred embodiments for fractionation of corn, the cornis prepared for extraction, and the oil is extracted from the preparedcorn with a solvent, providing an extracted corn-solvent mixture. Theextracted corn-solvent mixture is separated into at least two streams,one including an extract containing the oil and solvent, and anotherstream including the de-oiled corn solids and adsorbed solvent. Thesolvent preferably is separated from the oil in the extract. Thede-oiled corn solids may be desolventized to substantially remove thesolvent and provide de-oiled, desolventized corn solids. These cornsolids may be resuspended in water, and one or more of fiber, starch,and protein may be separated from the corn solids to produce cornproducts.

Alternatively or additionally, zein may be extracted from the de-oiledcorn solids with a solvent. The de-oiled corn solids-solvent mixture maybe separated into at least two streams, of which one is another extractcontaining the zein and solvent, and the other includes the de-oiled,de-zeined corn solids and adsorbed solvent. The solvent may be separatedfrom zein by membrane processing the extract. The de-oiled, de-zeinedcorn solids may be desolventized to remove the solvent, and thedesolventized, de-oiled, de-zeined corn solids may be resuspended inwater. Fiber, starch and protein may be separated from these cornsolids.

In yet another example process, corn is prepared for extraction, andzein is extracted from the prepared corn with a solvent, providing anextracted zein-solvent mixture. The extracted zein-solvent mixture isseparated into at least two streams, one including an extract containingthe zein and solvent, and another stream including the de-zeined cornsolids and adsorbed solvent. The solvent may be separated from the zeinin the zein-solvent mixture extract. The de-zeined corn solids may bedesolventized to substantially remove the solvent and provide de-zeined,desolventized corn solids. These corn solids may be resuspended inwater, and one or more of fiber, starch, and high-oil protein, such ashigh-oil corn gluten meal, may be separated from these solids.

In the above exemplary processes for separating corn, preparing the cornfor extraction may include, for example, dry-grinding or flaking thecorn. The extracting may include, for example, batch or continuousextracting, and the solvent may include a hydrocarbon, an alcohol, anethanol such as 95-100% ethanol (if oil is to be primarily extracted),60-90% oil (if zein is to be primarily extracted), or a solutionthereof. Separating the extracted corn-solvent mixture may include, forexample, centrifugation, filtration, or membrane filtration, andseparating the first solvent from the oil or from the zein may include,for example, nanofiltration or ultrafiltration. Solvent that isseparated may be recycled. Desolventizing the de-oiled corn solids,de-oiled, de-zeined corn solids, or de-zeined corn solids may use, forexample, vacuum, steam, air, and/or gas. Separating the fiber, starch,and/or protein from the de-oiled desolventized corn solids, thede-oiled, de-zeined, de-solventized corn solids, and/or the de-zeined,desolventized corn solids may include, for example, one or more grindingor separation steps.

FIG. 1 shows a flow of a corn product extraction application of theinvention to a dry mill ethanol plant. A preferred method of the presentinvention first extracts oil and/or zein from corn using, for example,the methods described in the '146 patent or by other methods. Corn orcorn processing by-products are the main raw material for preferredembodiments of this invention. For example, the corn inputs may includecorn (e.g., whole kernel or flaked corn), corn processing by-products(e.g., DDG, DDGS (distilled dried grains with solubles), corn glutenmeal, corn germ, or corn meal.

The raw material is ground and or sieved 10 to an appropriate size andshape. For example, a hammer mill or similar size reduction device, or aflaking machine is used to reduce the corn to an optimum particle sizefor extraction of oil with a particular solvent. If the raw material isa corn processing by-product, such as whole corn meal from a dry miller,this grinding or sieving step 10 may not be necessary. Preferably,moisture content of the corn should be 0-14% by weight.

The oil is extracted 12 using an appropriate solvent in an extractor.For example, alcohols such as ethanol, hydrocarbons such as hexane,acetone, and the like, including solutions thereof, may be used,provided the solvent efficiently extracts oil from the corn particles orflakes. The extraction may be batch or continuous extraction.

The resulting slurry including corn solids and the solvent is subjectedto a separation step 14, which may be, for example, centrifugation orfiltration. The slurry is separated into an extract 15 and a de-oiledresidue 17. The extract 15 is processed 16 through, for example,nanofiltration or reverse osmosis membranes to separate oil and/or otherextracted components from the solvent. The concentrated extract is sentto an evaporator 18 to remove the residual solvent. This removed solventmay be re-used in the extraction step 12. The crude corn oil 19preferably is refined 20, for example using methods well known in thevegetable oil industry.

Additionally, if ethanol, isopropanol, or similar solvent for extractingoil is used, a (usually) small amount of zein may be coextracted withoil in the extraction step 12, depending on the ethanol concentrationand other conditions. The zein can be recovered 22 prior to theseparation step 16 by processing the extract 15 with an ultrafiltrationmembrane, for example, and the permeate from recovery step 22 can besent for oil recovery in separation step 16. Exemplary methods andmembranes are described in the '146 patent.

The de-oiled corn solids 17 typically contain starch, protein, fiber,minor constituents of corn, and adsorbed solvent. These corn solids 17are desolventized 24 by any of various methods or apparatus such asvacuum, steam, air, or gas. Heat may be applied to facilitatedesolventizing the corn solids. The solvent vapor 13 may be reused inthe extraction step 12.

Though it is not necessary for ethanol or other solvent to be producedin the same facility (e.g., a plant) as the extraction methods describedherein, in-house ethanol may be preferred for economic reasons. Forexample, fermentation and distillation steps may be conducted to producean ethanol supply for the extraction step 12. However, ethanol or othersolvent for the extraction step 12 may be procured from outside sources.Costs of corn processing may be reduced by practicing extensiverecycling of the solvent via the membrane step 16, the evaporation step18, and/or the desolventizing step 24. The number of times the solventcan be recycled will depend on the level of impurities contained in theused solvent, and how it affects the extraction efficiency in theextraction step 12.

In preferred embodiments of the present invention, the de-oiled,desolventized corn solids 25 are made into a slurry by adding water,which may be either fresh water or, preferably, process water recycledfrom downstream operations. The amount of water added should besufficient to efficiently conduct a fiber separation and washing step30. This amount of water may be, for example, 1-10 parts by weight ofwater to one part by weight of the desolventized dry, de-oiled cornsolids 25. In conventional wet milling, this is usually a ratio of 3parts water to 1 part corn solids.

The slurry is sent to the fiber separation and washing step 30. Thisstep is preferred to obtain maximum starch recovery while minimizingfiber in the final starch and protein products. Fiber separation andwashing may include one or more individual steps, which are well knownto those of ordinary skill in the art. For example, it may be optimal tofirst grind the de-oiled, desolventized corn solids 25 to release someof the starch from the fiber. Any of several milling devices known tothose of ordinary skill in the corn wet milling art may be used torelease the starch. For example, Entoleter-type mills that sling thematerial against pins at high speed may be used to free the starch withminimum fiber breakup. Disk mills, with counter-rotating disk mills orwith only one disk rotating at high speed, can also be used.

The slurry of de-oiled, desolventized corn solids 25 preferably isseparated in the fiber separating step 30 by centrifugation and/orfiltration. A preferred method of fiber separation in corn millingemploys a 50-70 micron wedge-wire pressure-fed screen, such as the 120DSM screens made by Dorr-Oliver, of Milford, Conn. Wash water, usuallyrecycled process water from other milling steps, is introduced in thelast of 5-7 stages of the unit and flows counter-current to the fiber.The wash water emerges from the first fiber washing stage as an“undersize” fraction 35 with ideally all the starch and protein that wasin stream 25. Washed fiber 41 from the last stage of the fiberseparation step 30 is dilute, typically 5-20% solids. It is dewatered ina dewatering step 42 by mechanical devices or methods, such as by usingscreen centrifuges, screened reels, screw presses, belt presses, or thelike. The fiber after the dewatering step 42 may be dried 44 in a drier,or may be mixed with other streams before drying.

Water 43 from the fiber dewatering step 42 may contain some starch andprotein. To recover the soluble germ protein and other proteins that maybe present in the fiber wash water 43, it may be sent back to the fiberseparation step 30, or processed through an ultrafilter fitted with aprotein-retaining membrane 46. The retained solids stream 49 from themembrane 46 can be sent to a primary starch separator step 38, to agluten filter/drier 64, or it may be marketed as a protein product byitself. The clear permeate 47 from the membrane 46 can be used for thefiber separation step 30 or as process water.

After the fiber separation step 30, a stream 35, commonly referred to asthe “mill stream”, preferably contains only starch, protein (less thezein that may have been removed in the zein recovery step 22), and somesoluble impurities. The solids level of the mill stream 35 may be low(typically 5%-20% starch and 0.5-2% protein). The starch and protein 35preferably is thickened using a mill starch thickener (MST) 36. The MST36 may be a centrifuge or a membrane filtration system, for example, asdescribed in U.S. Pat. No. 6,648,978 to Liaw et al. The underflow (ifthickened with a centrifuge) or the retentate (if thickened with amembrane) 37 may have a 20%-30% solids concentration. This level ofsolids may facilitate better operation of a primary starch separationstep 38. The overflow or permeate 39 can be used as process water in theplant, which will also serve to recycle any solids that may be entrainedin the overflow or permeate.

It may be advantageous to first pass the starch and protein stream 35through a degritting step (not shown) prior to passing through the MST36. The degritting step removes the relatively fine gritty materialsthat may be in the stream 35. Manifolded cyclone systems, for example,can be used for this purpose.

The primary starch separation step 38 separates starch from the otherimpurities of the underflow or retentate 37 based on density differencesbetween the stream containing the protein and other impurities (whichhas a specific gravity of 1.1 or less) and the starch stream (which hasa typical specific gravity of 1.6). In a preferred embodiment, disk-typenozzle centrifuges are used for the starch separation step 38, such asthe BH-36B Primary Merco Centrifuge made by Dorr-Oliver. The overflow 61is the gluten stream containing 60-70% protein on a dry basis. Glutentypically refers to the two major insoluble fractions of corn, commonlytermed glutelin and zein. Gluten proteins are largely insoluble in waterat normal or acidic pH. Gluten may account for up to 80% of the totalnitrogen in corn.

The underflow 51 is a crude starch suspension typically containing30-35% solids, of which the protein and other impurities is 2-5% on adry basis. The starch underflow 51 is purified in a starch washing step52, which preferably includes a series of hydrocyclones in multiplestages. About 1.5-3 parts by weight of water per part of dry starch areused in a preferred hydrocyclone system. Alternatively, a membranemicrofiltration system such as that described by Shukla et al (Shukla,R., Tandon, R., Nguyen, M., and Cheryan, M., Microfiltration of starchsuspensions using a tubular stainless steel membrane. MembraneTechnology (Elsevier), No. 120:5-8, 2000) may be used. A preferredmicrofiltration system uses 1-5 feed volumes of diafiltration water foroptimal purification. This starch purification step 52 preferably is theonly point in the overall process where fresh water is used.

Starch wash water 53 from the starch washing step 52 may contain starch,protein and impurities. The wash water 53 can be used as process waterin other steps of the overall process, or it can be processed with amembrane filter 54 to recover some or substantially all of the solids ina retentate stream 55. The retentate stream 55 can be recycled for usein the primary starch separating step 38 or to a gluten thickening step62 depending on its composition. A permeate 57 from the membrane filter54 preferably is clean enough to be recycled to the starch washing stage52 if reverse osmosis or nanofiltration is used in the membrane step 54,or to the fiber washing stage 30 if an ultrafilter or microfilter isused in the membrane. In preferred embodiments of this invention, sincethere is no steeping of corn, the use of membrane filters 54 will reducewater usage in the plant. Typical reverse osmosis membranes include SW30from Dow-FimTec or CPA from Hydranautics or AG from GE-Osmonics.

The output from the starch washing step 52 is a concentrated starchstream 59. This starch stream 59 may be dried or used further in theplant as needed.

The gluten (protein and starch) stream 61 resulting from the starchseparation step 38 is processed in a gluten thickening step 62, whichmay employ a centrifuge in a conventional manner or a membrane filter,for example, as described in U.S. Pat. No. 5,968,585 to Liaw et al. Theconcentrated gluten stream may be sent to a gluten filter 64, and thendried for sale as corn gluten meal.

A dilute stream 63 from the gluten thickening step 62 and a dilutestream 65 from the gluten 64 may be used as process water in the plant.However, soluble germ proteins may be present in the gluten stream 61.There may thus be a significant quantity of protein in streams 63 and65. In conventional corn wet milling, such soluble germ proteins areused for corn gluten feed, which is a low-value product. In a preferredembodiment of the invention, stream 63 and/or stream 65 is passedthrough an ultrafilter 66 fitted with a protein-retaining membrane torecover substantially all the protein. The recovered protein can bemarketed as a corn protein fraction. The permeate from the ultrafilter66 preferably is used as process water.

Referring now to FIG. 2, a preferred process of the present inventionfor a plant focused on maximizing production of oil and zein isillustrated. Zein is an alcohol-soluble protein that has a multitude ofuses. Steps similar to those shown and discussed with respect to FIG. 1are labeled with like reference numerals.

Corn or corn processing by-products are the main raw material for thisinvention. The process for the oil extraction preferably is the same asdescribed for FIG. 1 and shown in FIG. 2 as steps 10 a through 20 a. Inthis embodiment, de-oiled corn solids 17 a are re-extracted (step 22 a)with 60-90% aqueous ethanol, more preferably 65-75% aqueous ethanol in asuitable extractor. If a solvent other than 95-100% aqueous ethanol isused for oil extraction, the de-oiled corn solids 17 a must bedesolventized before zein extraction (this desolventizing step is notshown in FIG. 2).

After the zein extraction step 22 a, the ethanol slurry is separated byfiltration or centrifugation into an extract 27 a and a de-oiled,de-zeined corn solids residue 23 a. The extract 27 a is processedthrough one or more ultrafiltration membranes 26 a to separate the zeinfrom the solvent and other low molecular weight impurities, as describedin the '146 patent. The concentrated zein is sent to a drier 28 a.

The de-oiled, de-zeined corn solids 23 a typically contain starch,protein other than zein, fiber, minor constituents of corn and adsorbedsolvent, and water. The corn solids 23 a are desolventized 24 a by anysuitable means, such as vacuum, steam, air or gas. Heat may be appliedto facilitate desolventizing the corn solids 23 a. The solvent vapor maybe reused in the extraction step 22 a.

Similar to the process shown in FIG. 1, resultantde-oiled-de-zeined-desolventized solids 25 a containing mainly starch,fiber and nonzein protein are processed to remove fiber and starch asillustrated in steps 30 a-64 a, which are similar to the stepsillustrated in FIG. 1.

FIG. 3 shows another example method of the present invention, whichincludes a zein extraction followed by processing of de-zeined cornsolids to provide one or more products. Steps similar and/or analogousto those shown and discussed with respect to FIG. 1 or FIG. 2 arelabeled with like reference numerals.

Corn or corn processing by-products are an example main raw material,which may undergo a grinding and/or sieving step 10 b. The zein isextracted 22 b, for example, using a solvent such as 60-90% ethanol (asa more particular, nonlimiting example, 65-75% ethanol, and even moreparticularly, 70% ethanol) in a suitable extractor. In an example methodaccording to FIG. 3, oil is not deliberately extracted from the inputcorn or corn products or by-products (though some oil may be extractedas a result of other process steps, and though oil can be deliberatelyextracted downstream after later steps).

After the zein extraction step 22 b, the ethanol slurry is separated,for example by filtration or centrifugation into an extract 27 bincluding zein, ethanol, and water, and a de-zeined (i.e., at least somezein removed) corn solids residue 23 b. The extract 27 b may beprocessed as described above, including processing through one or moreultrafiltration membranes 26 b to separate the zein from the solvent andother low molecular weight impurities, as described in the '146 patent.The concentrated zein may be sent to a drier 28 b. Separated ethanol maybe recycled (for example, for use in the solvent separation step 22 b).The vapor from the zein drier, containing ethanol and water, may also berecycled to various processing steps as needed or desired.

The residual corn solids 23 b typically contain oil, starch, proteinother than zein, fiber, minor constituents of corn and adsorbed solvent,and water. These corn solids are desolventized 24 b by any suitablemeans, such as methods or devices employing vacuum, steam, air, or gas.Heat may be applied to facilitate desolventizing the corn solids 23 b.The solvent vapor may be reused in the extraction step 22 b.

Similar to the example processes shown in FIGS. 1 and 2, resultantde-zeined-desolventized corn solids, still containing oil, can beprocessed to remove fiber and starch as illustrated in steps 30 b-64 b,which are similar to the analogous steps illustrated in FIGS. 1 and 2.However, due to the additional presence of oil in the corn solids 23 b,different end products can result. For example, after subjecting thede-zeined, desolventized corn solids 23 b to fiber separation andwashing 30 b, the resulting stream 35 b preferably contains oil, starch,protein (less the zein that may have been removed in the zein recoverystep 22 b), and some soluble impurities. Separated fiber 41 b may bedewatered 42 b and dried 44 b as described above. The starch and protein(with oil) 35 b can be thickened using the MST 36 b, as described above(a degritting step may be used prior to the MST, as also explainedabove).

The underflow or retentate 37 b from the MST 36 b undergoes a primarystarch separation step 38 b, resulting in gluten 61 b including protein,starch, and a significant concentration of oil. Following the glutenthickening 62 b (e.g., using a centrifuge or a membrane filter, asdescribed above) and subsequent gluten filtering 64 b and drying, ahigh-oil corn gluten meal results, which may be separately used or sold.

After the primary starch separation 38 b, the separated starch may bewashed 52 b, for example as described above, to provide a starch product59 b. Additional membrane filtering 54 b can be used on the starch washwater 53 b to recover solids 55 b that, if desired, can be recycled toupstream operations.

Preferred embodiments of the invention provide efficient, flexible andsimple processes for production of several products from corn. Further,a preferred process eliminates steeping of corn, which is one of themost troublesome and unpredictable steps in the conventional corn wetmilling process, and thus eliminates associated operations such as steepwater evaporators. Also preferably eliminated is the loss of corn solidsthat occurs due to leaching into the steep water.

Germ handling and separation preferably is completely eliminated. Crudecorn oil is produced in certain embodiments rather than germ, thusensuring a higher value to the corn processor. In addition, germproteins may be retained for more valuable use rather than being lostwith the germ (if the germ is sold to an outside oil processor) or putinto corn gluten feed. Zein may alternatively or additionally beproduced in some embodiments along with other coproducts that have oilas a significant component.

Preferably, germ proteins can be incorporated into corn gluten meal,which is a higher-value coproduct, or marketed as a separate product. Inparticular example embodiments, the corn gluten meal can also contain asignificant oil concentration, which may provide additional value.

The volume of low-value corn gluten feed preferably is reduced oreliminated. In a traditional corn wet mill, corn gluten feed istypically 21% protein (dry basis). This low-value product is used as arepository for otherwise unmarketable components or by-products or wastematter generated in a corn wet mill. Examples include corn steep liquor,fiber, germ proteins, “mud” from the clarification of dextrose,fermentation by-products, filter aid, and the like. Such a product mayalso be produced in embodiments of this invention by blending the fiberwith the protein streams if needed. A substantially pure corn fiber mayalso be generated, which may have higher market value than if it isincorporated into corn gluten feed.

Further, preferred embodiments of the invention reduce fresh water usagein the plant by using membrane technology in several places in theprocess train, and most preferably membrane technology is used torecover water and solids from the starch washing stage.

The various embodiments described in the present invention should not beconstrued as being restrictive in that other modifications,substitutions and alternatives to specific equipment and methods arepossible and would be appreciated by those of ordinary skill in the art.For example, it should be understood that “membrane” refers to theappropriate membrane, whether it is microfiltration, ultrafiltration,nanofiltration, or reverse osmosis. Further, it should be understoodthat diafiltration may be used when necessary to purify the solids, andthat combinations of these membrane techniques may be used. It will befurther understood that specific corn products can be selected forproduction, and thus it may not be necessary to produce all availableproducts in a particular process, nor to perform all steps to make suchcorn products available. Also, it should be understood that, thoughpreferred embodiments of the present invention provide severalopportunities for recycling of ethanol and/or process water, the presentinvention is not to be limited to processes that recycle at all possiblesteps.

While various embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions, and alternatives are apparent to one of ordinary skill inthe art. Such modifications, substitutions and alternatives can be madewithout departing from the spirit and scope of the invention, whichshould be determined from the appended claims.

Various features of the present invention are set forth in the pendingclaims.

1. A process for fractionation of corn, the process comprising: preparing the corn for extraction; extracting zein from the prepared corn with a solvent to provide an extracted zein-solvent mixture; separating the extracted zein-solvent mixture into at least a stream including an extract comprising the zein and solvent, and another stream comprising de-zeined corn solids and adsorbed solvent; separating zein from the solvent in the extract by membrane processing the extract; desolventizing the de-zeined corn solids to remove the adsorbed solvent; resuspending said desolventized, de-zeined corn solids in water; separating one or more of the fiber, starch, and protein from the resuspended desolventized, de-zeined corn solids to produce one or more corn products.
 2. The process of claim 1 wherein said preparing the corn for extraction comprises at least one of dry-grinding the corn and flaking the corn.
 3. The process of claim 1 wherein said extracting using the solvent comprises at least one of batch and continuous extracting.
 4. The process of claim 1 wherein the solvent comprises at least one of a hydrocarbon, an alcohol, an ethanol, and a solution of at least one of a hydrocarbon, an alcohol, an ethanol, and water.
 5. The process of claim 1 wherein said separating the extracted corn-solvent mixture uses at least one of centrifugation, filtration, and membrane filtration.
 6. The process of claim 1 wherein said separating the solvent from the zein comprises ultrafiltration.
 7. The process of claim 1 wherein said desolventizing the de-zeined corn solids uses at least one of vacuum, heat, steam, air and gas.
 8. The process of claim 1 wherein said separating one or more of the fiber, starch, and protein comprises separating fiber, and further comprising: washing the separated fiber.
 9. The process of claim 8 further comprising: dewatering and drying the separated and washed fiber.
 10. The process of claim 9 wherein the wash water from said fiber dewatering is membrane filtered to recover protein and starch.
 11. The process of claim 8 wherein the de-zeined, desolventized corn solids after said fiber separating comprise a suspension including substantially oil, starch, and protein in water, and further comprising: dewatering and thickening the suspension by at least one of a centrifuge, a membrane microfilter, and a membrane ultrafilter.
 12. The process of claim 11 wherein the suspension is separated into crude starch and a protein fraction including oil.
 13. The process of claim 12 further comprising: washing and purifying the crude starch using water.
 14. The process of claim 13 wherein said washing and purifying uses at least one of a hydrocyclone and a membrane microfilter.
 15. The process of claim 14, further comprising: passing the wash water from said starch purifying through at least one of a membrane, a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane and a microfiltration membrane, to recover clean water and concentrated solids.
 16. The process of claim 15 wherein the permeate from said passing through the membrane is recycled to upstream operations.
 17. The process of claim 16 further comprising: recycling retained solids from said passing through the membrane to upstream operations to recover the solids.
 18. The process of claim 12, further comprising: thickening the separated protein fraction in a gluten thickener, wherein the gluten thickener includes at least one of a centrifuge, a membrane microfilter, and an ultrafilter designed to retain substantially all proteins and starch.
 19. The process of claim 18 wherein said thickening uses a centrifuge, and wherein the overflow from the centrifuge is sent to at least one of a membrane microfilter, an ultrafilter, and a nanofilter to recover substantially all the protein.
 20. The process of claim 19 wherein said thickening uses a gluten filter, and further comprising: membrane processing the filtrate from the gluten filter using at least one of reverse osmosis, nanofiltration, ultrafiltration, and microfiltration to recover protein with oil. 